Brake booster

ABSTRACT

The invention relates to a brake-booster comprising a casing (10) within which is found a piston structure which, with the help of an unrolling membrane (12), defines a front chamber (16) permanently connected to a partial vacuum source by a valve (17) and a back chamber (16) selectively connected to the front chamber (16) or to the atmosphere via a valve means (34) when a control rod (30) is actuated, and a device (36) for fastening the booster on a wall (38) adjacent to a first face of the casing (10). According to the invention, apertures (50, 60) are made in the piston structure (14) and in a second face of the casing (10) and are aligned in the axial direction of the booster so as to permit the actuation of the fastening device (36) through the aperture (60) made in the second face of the casing (10).

The present invention relates to pneumatic boosters, more particularlyof the type of those which are used in order to provide assistance tothe braking of motor vehicles.

Boosters of this type comprise in a conventional manner a casing withinwhich is found at least one piston structure which, with the help of anunrolling membrane, defines at least one front chamber permanentlyconnected to a partial vacuum source and at least one back chamberconnected selectively to the front chamber or to the atmosphere via avalve means when a control rod is actuated, and a device for fasteningthe booster on a wall adjacent to a first face of the casing.

The booster is mounted, as a general rule, on the apron of the enginecompartment of the vehicle by mounting screws which are fastened on theback part of the casing on the apron side. It is therefore necessary totighten nuts onto the mounting screws on the vehicle passengercompartment side. This operation presents disadvantages for themanufacturers during the production of the vehicle, because it requiresthe execution of operations simultaneously on the engine compartmentside and on the passenger compartment side.

The object of the present invention is therefore to provide abrake-booster which permits mounting thereof in a vehicle by workingsolely on the side of the wall where the booster is mounted.

According to the invention, this result is obtained by making aperturesin the piston structure and in a second face of the casing, theseapertures being aligned in the axial direction of the booster so as topermit the actuation of the fastening device through the aperture madein the second face of the casing, the aperture made in the pistonstructure receiving a closing member.

The invention will now be described by way of example with reference tothe accompanying drawings in which:

FIG. 1 is a view in longitudinal section of a brake-booster, constructedin conventional manner in the upper half of this Figure and constructedaccording to a first embodiment of the invention in the lower half ofthis Figure.

FIG. 2 is a view similar to that of FIG. 1 and shows in its lower half asecond embodiment of the invention.

FIG. 3 gives a partial view of a variant of FIG. 2.

FIG. 4 is a view in longitudinal section of a brake-booster mounted intandem, produced in accordance with one embodiment of the invention, and

FIG. 5 is a view in longitudinal section of a brake-booster with anadditional chamber, produced in accordance with one embodiment of theinvention.

FIG. 1 shows a brake-booster intended to be placed, in a usual manner,between the brake pedal of a vehicle and the master cylinder controllingthe hydraulic brake system. By convention, the part of the boosterdirected towards the master cylinder will be termed "front" and the partof the booster directed towards the brake pedal, "back".

The booster comprises a shell-shaped outer casing 10 presentingsubstantially a symmetry of revolution about an axis X-X'. A flexiblemembrane in elastomer 12, reinforced in its central part by a metal disk14 also termed skirt, defines within the space delimited by the casing10 a front chamber 16 and a back chamber 18. The front chamber 16 ispermanently connected to a partial vacuum source by a vacuum retainingvalve 17 disposed in an aperture of the front wall of the casing 10. Theouter peripheral edge of the membrane 12 is secured in leaktight manneronto the outer casing 10. The inner peripheral edge of this membraneterminates with a bead received in leaktight manner in an annular grooveformed on the outer peripheral surface of a piston hub 20 disposed alongthe axis X-X' of the booster. This hub 20 extends backwards in the shapeof a tubular part 22 which passes in leaktight manner through the backwall of the casing 10. The leaktightness of this passing-through isensured by a reinforced annular seal 24 which is fastened by a ring 26in a tubular central part extending backwards the back wall of thecasing 10.

A compression spring 28 interposed between the skirt 14 and the frontwall of the outer casing 10 normally retains the skirt 14 in a rear restposition shown in FIG. 1, in which the back chamber 18 occupies itsminimal volume and the front chamber 16 its maximal volume.

In a known manner, the tubular part 22 of the hub 20 receives a controlrod 30 intended to be connected to the brake pedal (not shown). Theother end of the rod 30 comprises a plunger 32 which is intended, duringoperation of the booster, to actuate a conventional valve means 34 whichcontrols in a known manner the passage of air to the back chamber 18 orfrom the back chamber 18 to the front chamber 16.

The booster further comprises, as shown in the upper half of FIG. 1,devices 36 for fastening on a wall 38 of the vehicle, such for exampleas the apron separating the passenger compartment from the enginecompartment. The fastening devices 36 are conventionally constituted byscrews the head 82 of each of which is situated in the back chamber 18and the shank 40 of each of which is crimped, at its end close to thehead 82, into the casing 10. Thus, during the mounting on the vehicle,the booster is presented on the apron through the engine compartment sothat the shanks 40 enter the apertures 42 of the apron, and then,through the passenger compartment, a nut is screwed onto the thread ofthe screw 36, with the well-known attendant difficulties for theoperator who cannot be simultaneously inside and outside the passengercompartment of the vehicle, the access to the fastening zone of theassembly, on the passenger compartment side, being moreover extremelydifficult.

The present invention has precisely the object of obviating thesedisadvantages by providing a booster greatly facilitating the operationsof mounting and of removal and in particular enabling the operator tocarry out all of the operations of mounting or of removal, whileremaining solely on the side of the wall of the vehicle where thebraking assembly is installed.

In order to do this, as shown in the lower half of FIG. 1, the aperture42 in the apron 38 is shaped so as to be capable of cooperating with thethread of a screw. As shown, the apron 38 may be formed so as to presentaround the aperture 42 a tubular part 44 extending backwards into thepassenger compartment and possessing an inner tapping. As a variant,provision may be made for a nut to be made integral with the apron 38.

The fastening device 36 is constituted by a screw the head 82 of whichis situated in the back chamber 18 and the shank 40 of which passesthrough an aperture 46 made in the back face of the casing 10. The screw36 is received in the aperture 46 so as to be free in rotation in thisaperture, but is imprisoned by it, that is to say that it cannot beextracted from it, in the manner of captive screws.

An aperture 50 is made in the piston structure, and more precisely inthe skirt 14, so that this aperture 50 is aligned in the axial directionwith the aperture 46 and the screw 36 and a closing member is disposedin this aperture. For example, at this place on the skirt, the unrollingmembrane 12 is shaped so as to form a valve 52. In the example shown,the membrane 12 comprises a flange 54 in order to anchor the membraneonto the skirt 14, and, extending from this flange 54, a tubular part 56extending backwards, and whose back edges normally remain flattenedagainst one another. Such a design is known by the name duckbill valve.The skirt 15 may advantageously be shaped in this place with aprojection in order to facilitate the functioning of the valve 52.

Lastly, an aperture 60 is made in the front wall of the casing 10, so asto be aligned in the axial direction with the aperture 50 comprising thevalve 52 and the aperture 46 containing the screw 36.

From the preceding explanations, it will have been understood how thebooster can be installed on the apron of the vehicle. The booster ispresented onto the apron 38 through the engine compartment so that theshanks 40 of the screws 36 fit into the apertures 42 of the apron 38.Owing to their design, they remain imprisoned by the apertures 46 of thecasing 10, and come to rest against the tubular part 44, or the nut,disposed behind the aperture 42. At that moment, the operator insertsthrough the aperture 60 in the front wall of the booster a tighteningtool the head of which entering the booster has a shape complementary tothat of the head of the screw 36. In the example shown, the head 82 ofthe screw 36 is shaped with a blind recess, for example in the form of ahollow hexagon. In continuing its insertion, the head of the tool willencounter the valve 52 and separate the edges of the tubular part 56 soas to arrive at the head 82 of the screw 36. It is then sufficient forthe operator to turn the tool so as to screw the screw 36 into the part44 of the apron 38, or into the nut integral with the apron. Once thescrew has been put into place and tightened with the required tighteningtorque, the operator can withdraw the tool from the booster. During thiswithdrawal, the tool slides along the tubular part 56 of the membrane 12and, as the head of the tool passes progressively through this tubularpart, the edges of this part come together and resume the position shownin FIG. 1.

When the tool is completely removed from the booster, the aperture 60 inthe front wall can then be closed off so as to render the boosteroperational. Provision may be made to dispose a plug 62 in thisaperture, as shown. Provision may also be made to close off the aperture60 by means of the vacuum retaining valve 17 which will then be disposedin this place rather than in the position shown. Provision may also bemade for the closing-off of the aperture 60 to be effected by the flangefor mounting a master cylinder (not shown) on the front face of thebooster. The same operation is repeated with the other fastening screwor screws of the booster (generally two in number) so as to complete theinstallation of the booster.

It can therefore be clearly seen that, according to the invention, abooster has been constructed the entire installation of which is carriedout by working solely from the side of the wall where the booster isinstalled. This therefore results in a mounting and a removal of thebooster which are particularly easy, even capable of being automated bymeans of industrial robots.

FIG. 2 shows an example of a second embodiment of the invention. In thisFigure, the same members as those of FIG. 1 bear the same referencenumbers. According to this embodiment, the aperture 46 cooperating withthe screw 36 in the back wall, and the aperture 60 and the plug 62 inthe front wall, are identical to those of the preceding embodiment.

The aperture 50 in the skirt 14 receives a closing member in the form ofan intermediate member 64. In a more precise manner, the aperture 50 isformed at the top of a projection 66 of the skirt 14 the convexity ofwhich is turned forwards. The membrane 12 is shaped with a bead 68fitting the concave shape of the projection 66 and delimiting anaperture 70 coaxial with the aperture 50. In this aperture 70 isreceived in leaktight manner the cylindrical central part 72 of theintermediate member 64.

The front part 74 of the intermediate member is situated in the frontchamber 16 of the booster and is shaped like a nut, being for examplehexagonal. The back part 76 of the intermediate member is situated inthe back chamber 18 of the booster and is also shaped like a nut, beingfor example hexagonal, of shape complementary to that of the blindrecess of the head 82 of the screw 36, for example in the form of ahollow hexagon. Between the front part 74 and the central part 72 isformed a groove 78, and between the central part 72 and the back part 76is formed a swelling defining a front step 80 and a back step 84.

The installation on the vehicle of the booster according to thisembodiment is completely similar to that which was previously described.Once the booster is ready, that is to say once the shanks 40 of thescrews 36 are engaged in the apertures 42 of the apron 38, the operatorinserts through the aperture 60 a tool whose head entering the boosterhas a shape complementary to that of the front part 74 of theintermediate member 64. The tool then causes the intermediate member 64to move backwards if it was in forward position, and the back part 76 ofthe intermediate member comes to fit into the head 82 of the screw 36until the step 84 comes to be stopped against the head 82.

The operator then has only to turn the tool in order to screw the screw36, by means of the intermediate member 64, into the tubular part 44 ofthe apron 38, or into the nut integral with the apron. Once the screw isput into place and tightened with the required tightening torque, theoperator can withdraw the tool from the booster. At the start of thisphase of withdrawal of the tool, the latter, which comprises meanscooperating with the groove 78, carries along with it towards the frontthe intermediate member 64 until the front step 80 comes to be stoppedagainst the bead 68 of the membrane 12. The means of the tool whichcooperate with the groove 78 are then retracted manually orautomatically when a threshold of tractive effort is exceeded, and thehead of the tool can then be disengaged from the front part 74 of theintermediate member 64 and extracted from the booster.

During the movement of withdrawal of the tool, it will be seen thereforethat the back part 76 of the intermediate member 64 has been disengagedfrom the head 82 of the screw 36. This has the object of preventingslight eccentricities of the intermediate member 64, due to themovements of the skirt 14 during successive actuations of the booster,with respect to the head of the screw 36, from creating interferencesbetween these two parts which would disturb the return to the rear restposition of the piston structure.

The aperture 60 in the front wall of the casing can then be closed offas previously with a plug 62, a vacuum retaining valve 17 or the flangefor mounting a master cylinder on the booster.

Here again, it can be seen that a booster has been constructed theentire installation of which is carried out by working solely from theside of the wall where the booster is installed.

A variant of the embodiment according to FIG. 2 is shown in FIG. 3,where the intermediate member 64 is seen to be constituted by a blindtube of which the part 84 situated in the direction of the screw 36 ison the outside in the form of a hexagon complementary to the hollowhexagonal shape of the head 82 of the screw 36, and on the inside in theform of a hollow hexagon.

The tube 64 also comprises a fold 86, forming a flange on the outside,and a groove on the inside. The tightening tool 88 itself comprises atits end entering the booster a retractable retaining ring 90 and ahexagonal shape cooperating with the hollow hexagonal shape of thebottom of the tube 64. This tool, once inserted into the booster, hasits hexagon cooperating with that of the screw 36, through the tube 64,and its retaining ring 90 clipped into the groove of the fold 86.

When the tightening of the screw 36 is completed, the tool 88 iswithdrawn, and in this movement effects the withdrawal towards the frontof the tube 64, by means of the retaining ring 90, until the flange ofthe fold 86 bears against the bead 68. The tool is then withdrawncompletely, owing to the retraction of the retaining ring 90, and theaperture 60 plugged as previously.

The invention also applies to double or tandem-mounted pneumaticboosters as have been represented in FIG. 4. Such a boosterconventionally comprises an outer casing 10, whose inside is divided bya fixed partition 11 into a front volume A and a back volume B. The backvolume B comprises the same elements as those which have been describedwith reference to FIG. 2 and which bear the same reference numerals. Thefront volume A comprises elements similar to those which were describedwith reference to FIG. 2, and which bear the same reference numeralsincreased by 100. With these conventions, it is seen that the frontvolume A is divided into a front chamber 116 and a back chamber 118 by aflexible membrane 112 reinforced in its central part by a metal disc 114also called a skirt.

The front chamber 116 is permanently connected to a vacuum source via avacuum-retaining valve 17 arranged in an aperture of the front wall ofthe casing 10. The outer peripheral edge of the membrane 112 is fixed inleaktight manner to the outer casing 10. The inner peripheral edge ofthis membrane ends in a bead received in leaktight manner in an annulargroove formed on the outer peripheral surface of a piston hub 120disposed along the axis X-X' of the booster.

This hub 120 extends backward in the shape of a tubular part 122 whichpasses in leaktight manner through the fixed partition 11. The tubularpart 122 of the hub 120 is secured, for example by screwing, to the hub20. The two skirts 14 and 114 are thus secured, and the compressionspring 28 interposed between the skirt 114 and the front wall of theouter casing 10 normally maintains the skirts 14 and 114 in a rear restposition illustrated in FIG. 4, in which the back chambers 18 and 118occupy their minimum volume and the front chambers 16 and 116 occupytheir maximum volume.

As in the embodiments described previously, the apron 38 is shaped so asto be able to interact with the thread of a screw 36 trapped in theaperture 46 made in the back face of the casing 10. The skirt 14 isformed with the aperture 50 closed off by the intermediate member 64.

In the same way, the skirt 114 is formed with a boss 166 whose convexityis turned forwards, and at the top of which there is formed an aperture150. The membrane 112 is formed with a bead 168 matching the concaveshape of the boss 166 and delimiting an aperture 170 coaxial with theapertures 50 and 150.

The fixed partition 11 is formed with an aperture 13 coaxial with theapertures 50 and 150 and equipped with a seal 15. A tube 17 slides inleaktight manner in the apertures 150 and 13, and has a length slightlygreater than the maximum travel of the skirts 14 and 114.

The installation of the booster of FIG. 4 in the vehicle emerges clearlyfrom the preceding description. Once the booster is ready, that is tosay once the shanks of the screw 36 are engaged in the apertures 42 ofthe apron 38, the operator introduces through the aperture 60 a toolwhose head penetrating the booster has a shape complementary to that ofthe front part of the intermediate member 64. The tool passes throughthe tube 17 and is engaged in the head of the screw 36, which it thensuffices to screw.

The operator may withdraw the tool as previously and close off theaperture 60.

The front and back edges of the tube 17 may advantageously be foldedover to ensure that the latter does not lose contact with the apertures13 and 150. Of course, a valve 52 or a blind tube may be used in placeof the intermediate member 64. One additional advantage of thisembodiment resides in the fact that, once the tandem booster isinstalled in the vehicle, the tube 17 provides the communication betweenthe front chambers 16 and 116 of the front and back volumes A and B.

The invention may also be applied to boosters with an additionalchamber, for example of the type described in the document U.S. Pat. No.5,044,255 to which reference may be made and which is represented inFIG. 5.

According to this type of booster, an auxiliary annular housing 25 isfastened to the skirt 14 and projects into the front chamber 16.

An annular piston 27 internally divides this auxiliary housing 25 intotwo chambers 29 and 31 in sealed manner by virtue of an auxiliarymembrane 33. The annular piston 27 is mounted fixed with respect to thecasing 10. More precisely, in order to implement the present invention,the annular piston 27 is formed with an extension of overall cylindricalshape 35 extending backward, fixed to the back wall of the casing 10,around the aperture 46 receiving the screw 36. The unrolling membrane 12is formed with an aperture whose periphery 37 is fastened in leaktightmanner around the cylindrical extension 35 to provide sealing betweenthe back chamber 18 and the chamber 29 of the housing 25.

Coaxially to the cylindrical extension 35, the skirt 14 is formed withan aperture 50 receiving, as has been shown, an intermediate member 64,a valve 52 or a blind tube as in the preceding embodiments. The boosterwith an additional chamber may thus be mounted as already explainedpreviously.

Of course, the invention is not limited to the embodiments which havebeen described by way of example, but is capable of receiving numerousvariants which will be apparent to a person skilled in the art. It is inthis manner for example that, for some applications where the booster isrequired to be installed in the passenger compartment of the vehicle,the invention is applied by disposing the fastening device on the frontwall of the booster and the aperture 60 on the back wall of the booster.In these cases, the embodiment of FIG. 2 will be preferred and theinstallation will be carried out with the compression spring 28 havingbeen completely compressed so that the piston structure occupies itsextreme forward position. Moreover, the tightening tool 88 may bepre-installed in the booster, as shown in FIG. 3, so that, wheninstalling the booster on the vehicle, the operator will have only tooperate the tightening tool in rotation and to withdraw it once thetightening has been carried out. This arrangement thus spares theoperator from inserting the tool into the booster, searching for thealignment and the precise positioning of the tightening tool withrespect to the intermediate member 64. Similarly, the valve of theembodiment of FIG. 1 may be constructed with the help of a rigid insertburied in the membrane so as to form a rocking closing device, comingnormally to plug the aperture made in the skirt owing to the resilienceof the material constituting the membrane, and opening by rotation aboutone of its sides under the effect of the external force caused by theintroduction of the tightening tool into the booster.

We claim:
 1. A brake booster comprising a casing (10) within which is at least one piston structure which, with the help of an unrolling membrane (12), defines at least one front chamber (16) connected permanently to a vacuum source via a valve (17) and at least one back chamber (18) connected selectively to the front chamber (16) or to atmosphere via valve means (34) when a control rod (30) is actuated, and a fastening device (36) for fastening the booster on a wall (38) adjacent to a first face of the casing (10), apertures (50, 60) located in a piston structure (14) and in a second face of the casing (10) and aligned in an axial direction of the booster so as to permit the actuation of the fastening device (36) through the aperture (60) in the second face of the casing (10), characterized in that the aperture (50) in the piston structure (14) receives a closing member (52, 64) integral with the piston structure and movable with the piston structure.
 2. Booster according to claim 1, characterized in that the fastening device (36) is a screw (36) received in an aperture (46) of the first face of the casing (10) so as to be free in rotation in this aperture (46) and to be imprisoned by this aperture (46).
 3. Booster according to claim 2, characterized in that the screw (36) comprises a head having a shape complementary to that of a tightening tool.
 4. Booster according to claim 3, characterized in that the closing member is a valve (52).
 5. Booster according to claim 4, characterized in that the valve (52) is formed by a tubular part (56) of the unrolling membrane (12) whose edges remote from the piston structure (14) normally remain flattened against one another.
 6. Booster according to claim 3, characterized in that the closing member is an intermediate member (64) received in leaktight manner in an aperture (70) of the piston structure (14).
 7. Booster according to claim 6, characterized in that the intermediate member (64) comprises a first end part (74) having a shape complementary to that of the head of the tightening tool and a second end part (76) having a shape complementary to that of the head (82) and of the screw (36).
 8. Booster according to claim 6, characterized in that the intermediate member (64) is constituted by a blind tube a part (84) of which situated in the direction of the screw (36) has a shape complementary to the shape of the head (82) of the screw (36).
 9. Booster according to claim 8, characterized in that the tube (64) comprises a fold (86) forming an outer flange and an inner groove.
 10. Booster according to claim 9, characterized in that a retaining ring (90) is resiliently mounted on the tightening tool (88) and is received in the inner groove of the tube (64).
 11. Booster according to claim 1, characterized in that an auxiliary housing (25) is secured to the piston structure (14) and projects into the front chamber (16), an auxiliary piston (27) internally dividing the auxiliary housing (25) in leaktight manner into two chambers (29, 31) by virtue of an auxiliary membrane (33), the auxiliary piston (27) being mounted fixed with respect to the casing (10) by means of at least one cylindrical extension (35) extending backward and fastened to the casing (10) around the fastening means (36), the cylindrical extension (35) being coaxial with the aperture (50) made in the piston structure (14).
 12. Booster according to claim 1, additionally comprising a fixed partition (1) delimiting, inside the casing (10), a front volume (A) and a back volume (B), the front volume being divided in leaktight manner into a front chamber (116) and a back chamber (118) by a second piston structure (114) secured to the piston structure (14) of the back volume (B) by means of a tubular part (122) which traverses, in leaktight manner, the fixed partition (11), characterized in that apertures (13, 150) are in the fixed partition (11) and in the second piston structure (114), aligned in the axial direction of the booster with the apertures (50, 60) made in the piston structure (14) of the back volume (B) and in the second face of the casing (10) and receiving a tube (17) with leaktight sliding.
 13. Booster according to any one of the preceding claims, characterized in that the aperture (60) made in the second face of the casing (10) is closed off by a plug (62).
 14. Booster according to any one of claims 2 to 12 and 1, characterized in that the aperture (60) made in the second face of the casing (10) is closed off by the valve (17). 